Note 2 - Revenue and Product Costs - Contract Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Balance at January 1, 2022	$ 265
Balance at March 31, 2022	282
Current portion	121	$ 155
Long-term portion	161	$ 110
Customer Deposits [Member]
Balance at January 1, 2022	43
Additions, net	0
Transfer to revenue	(43)
Balance at March 31, 2022	0
Current portion	0
Long-term portion	0
Deferred Revenue [Member]
Balance at January 1, 2022	265
Additions, net	56
Transfer to revenue	(39)
Balance at March 31, 2022	282
Current portion	121
Long-term portion	$ 161